A. Field of the Invention
The present invention relates generally to power systems and, more particularly, to the initial application of power to electrical systems.
B. Description of Related Art
In certain electrical systems, such as computer and communication systems, different parts of the system may be designed to be powered from different power sources. For example, a computer system may include a first component designed to operate with a 1.5 volt source, a second component designed to operate with a 3.3 volt source, and a third component designed to operate with a 10 volt source. Typically, such electrical systems provide the power to each component through a series of regulators that convert power from a main power supply to a power level appropriate for each component. Because each regulator draws from the same main power supply, the different voltages (or currents) supplied to the components are not fully independent of one another. That is, power fluctuations caused by one of the components can affect the power supplied to the other components. This effect can be exacerbated by the fact that the components may be further tied to one another through electrical connections at the signal level.
Due to this lack of isolation between the components of the electrical system, when initially powering-up each component, it is desirable to sequentially power up each component and wait until the power to the component stabilizes before supplying power to the next component. In this manner, large, potentially damaging power spikes can be avoided. This can be particularly important when dealing with sensitive electronic equipment.
Conventional sequential power-up circuits were either manually operated by a user or automated through a simple on/off architecture that delayed power to each component using a resistor/capacitor structure. Such circuits can be inadequate for highly sensitive components in modern electrical systems.
Thus, there is a need in the art to improve power-up sequencing when supplying varying power levels to multiple components in an electrical system.
Systems and methods consistent with the present invention address this need by providing a reliable power-up sequencing circuit that monitors and sequentially enables power to components in an electrical system.
In accordance with an aspect of the present invention as embodied and broadly described herein, a voltage sequencing circuit is described that includes multiple elements. These elements include electrical power sources configured to supply power to electrical components having differing power requirements. Additionally, a power monitor connects to the outputs of the electrical power sources to detect failures in the electrical power sources. A decision logic component connects to the electrical power sources and to an output of the power monitor. The decision logic performs a power-up sequence by sequentially enabling the electrical power sources and verifying, based on outputs from the power monitor, that an enabled one of the electrical power sources is stable before enabling a next one of the electrical power sources.
A method consistent with another aspect of the present invention provides power-up services to an electrical system from multiple different power sources. The method includes: (a) enabling a first of the power sources to source power to the electrical system; (b) waiting a predetermined period for the power from the first of the power sources to settle; and (c) beginning to monitor an output of the first of the power sources for a failure in the sourced power. Additionally, (a), (b) and (c) are repeated for each additional power source, and all of the power sources are disabled when any of the monitored power sources fail.